Four fish rhabdoviruses have been identified as the etiological agents of economically important diseases in fish (carp, pike, trout and salmon) as evidenced by losses incurred in both European or American fish hatcheries. Initial studies have indicated that structurally the viruses differ both from each other and from the well-studied rhabdovirus vesicular stomatitis virus. The nature of these differences and their effect upon the respective virus infections and replication processes will be studied. The molecular approaches will be undertaken in order to gain an insight into how these viruses replicate in permissive cells.